Process for reducing iron ores at low temperatures



April 12, 1960 K, voN HAKEN 2,932,563 PROCESS FOR REDUCING IRON ORES AT LOW TEMPERATURES Filed Sept. 16. 1955 3 Sheets-Sheet l April 12, 1960 K. VON HAKEN 2,932,563

PROCESS FOR REDUCING IRON ORES AT LOW TEMPERATURES Filed Sept. 16. 1955 3 Sheetshet 2 wv; Ivre/#0H April l2, 1960 K. voN HAKEN 2,932,563

PRocEss FOR REDUCING IRON oREs AT Low TEMPERATURES Filed Sept. 16. 1955 3 Sheets-Sheet 5 WWW United States Patent4 O PROCESSEUR REDUCING IRON ORES AT LOW TEMPERATURES Kurd von Haken, Murnau, Upper Bavaria, Germany, as-

signor of one-third to Johannes Bernhard Hahn, Munich, Germany Application September 16, 1955, Serial No. 534,685 Claims priority, application Germany October 13, 1954 3 Claims. (Cl. 75-26) Starting from cinder of ores such as brown iron ores or taconites which can easily be cindered, e.g. hematite, gotite, limonite, an oxidation process to brown magnetic fy-Fe203 is carried out. This oxidation has to be carried out at temperatures of from 330 C. to 270 C. with cooling; or else the y-form becomes again the a-form.

This 'y-form can easily be magnetically `separated from the gangue. A mechanical process in the disintegrator can be added.

During the reduction to iron by carbon monoxide, CO, already at a temperature of 160 C., a black iron coating is produced on the surface of this fy-FezOa. The renewed reduction with CO takes place slowly. This can be explained by the slow escape ofthe developed CO2 from the micro-crystallites of the iron oxides.

'Ihe object of the invention is a process by which the grains or powder of iron oxide are brought into contact with the dust of soft coal containing bitumen or gas, by mixing and whirling them at reduction temperatures of from 350 C.-540 C.

Other iron oxides, iron ores or iron concentrates too are reduced by this reducing process at increasing temperatures to 640 C.

In order to continue the contact between coal and iron oxide the reduction is carried out under a perpetual whirling in a whirl layer process; simultaneously the burning of the coal or carbon monoxide is carried out at low temperatures wi-thout annealing.

It is already known that with higher temperatures than 330 C. by oxidation of cinder FeBO., a'loose black magnetic powder is obtained; but this product cannot be so easily and directly reduced from the micro-crystalline surface to iron as the brown fy-Fe203. All parts of the product form a ball during the reduction with FegO., forming ferrie oxide FeO while sintering.

In the drawings `the reduction process is illustrated byV diagram curves and by an embodiment of the furnace A used for the execution of the process.

Fig. 1 shows diagram curves according to the coordinating system, the ordinates representing the temperatures and the abscissas the yield of pure iron;

Fig. 2 shows a whirl layer furnace for the execution of the process in vertical section through the whirl layers;

Fig. 3 shows the same whirl layer furnace as in Fig. 2 in vertical section rectangular to the section plane of Fig. 2.

In Fig. 1 the curves 1 and 2 are concerned with a- Fe203, a thin nonrotating layer of which has been treated with a gas containing 30% of CO for 15 or 30 minutes, at increasing temperatures. At a temperature of 400 C. the' formation of FeBO., can be observed.V Just below 600 C. the production of ferric oxide FeO begins. Above the line A-B a stronger sinter zoneis formed under the inuence of FeO, by which the reduction process is nearly impossible.

By a quick treatment with y-FeZOS according to `curve 3 in Fig. 1 one gets into Ithis sintering zone within 15 minutes. Working for 30 minutes, curve 4, by `slowly increasing the temperatures, a pure iron powder will be obtained.

By treating -Fe203 in pellets with a whirl layer process at about 725 C. with the addition of CO, 40% pure iron was obtained in 7 minutes. By using loose FesO., the result was 50% pure iron.

These two experiments showed 3 or 4 times the speed of reduction of the non-whirled powder.

At the reduction of y-FezOa the use of the whirl layer process with addition of coal leads, within 10 minutes, according Ito the lower curve 6, to the production of iron at a temperature of about 540 C. By using a mixture with 50% ot-Fe203 this occurs at a temperature of 640 C. according to curve 5.

The vertical section of the whirl layer furnace 11 in Figs. 2 and 3 is divided into horizontal layers 12 the top layer contains dust separators 13 below the pneumatic introduction means 14 for ry-FeO coming from the dust tank 15 with addition of gas above the uppermost layer of the distribution channels 16. The material introduced at the device 1'4 will be heated by the gas coming from below and oppositely directed to the falling down iron oxide powder meshed with gas (for 1 ton of iron 500 c.b. m. of gas), containing mainly CO, CO2, H and N. CO will be burned at low temperature by the iron oxide to CO2, so that it will not be lost.

The iron oxide material y-Fe203 falls to the top whirl layers 12 and between those through the open intermediate spaces 17 to the lower whirl layers 12. Above each channel 16 a spaced cover with upwardly to the vertical central line of the channel inclined surfaces is disposed.

By a blowing engine 18 through the feed pipes 19 with throttle valves 20 which are opened at intervals by a moving endless chain 21 with an automatic driving mechanism carbon dust from dust tanks 2.2 with injectors 23 and gas 15 are advanced through the 'tubes 24 of the whirl channels 16 in one row of channels 16 after the other. The material is whirled up by gas stream. During the time between the intervals of opening the throttle valves 20 the material falls to the lower layers 12 through the intermediate spaces 17. Finally the reduced iron powder gets to the bottom through a tube cooler 25 where it is cooled below 100 C. and through a funnel 26 it is Itransported out of the furnace by any hydraulic means 34. Through a tube 27 bare annealing gas is introduced -into the lower part of the furnace. Coal dust and grains of the material to be reduced will be introduced together with the gas pneumatically `from tanks 14 through tubes 29 in the necessary quantity.

In the lowest layer 12 `before the cooler 25 the material will be heated to a higher degree with gas flames 30, and soda and lime dust from tank 31. with injector 33 will be introduced together with gas through pipe 32. Thus a thin coating like glass is formed with ashes and the remainder of the gangue at about 700 C. on the surface of the iron dust. After its cooling the material Vis slightly ground in disintegrators and then separated in the magnetic separator as pure iron powder, or it will be brought directly to a foundry. The gas for heating and processing is produced in a special gas generator.

coal with respect to the weight of iron is necessary; if carbon is used in form of CO the double quantity of this gaseous carbon is necessary for the same weight of iron.

The reduction of other iron ores such as magnetite and pyrite residue can be carried out in such a way, that those are pelletised from powder with at least 30% of 'y-Fe oxide together with coal dust and are afterwards burned in a blast furnacepor low shaft furnace or cupola. The 'advantage is that'the reduction process `itself takes place at low temperatures and that Ionly iron has to be melted besides the gangue without contents Vof oxygen. In that `way the use of `burning material is limited.

The continuous formation of iron starting from the Vsurface is noticed, while brown 'y-FezOa can 'be observed in the interior o f the grains.

The process of gaining the brown 'y-iron oxide for the production of pure iron, starting from cinder Fe3O4 can .only be carried out at falling temperatures from 350 C. to 270 C. It is preferred to use the same whirl layer furnace. The material has to be intensively cooled, as much heat will be released through this process.

The characteristic part of the invention consists in carrying out the continuous reduction on a basis of the contact of 'y-Fe203 with carbon dust at temperatures lying `below the zone of sinter, line A-B, preferably at temperatures rising from 350 C. to 540 C.; by adding other iron oxides rising to about 640 C.

In this case the reduction takes place in about minutes.

Y `Impurities, as far as they enter the iron at those temperatures, have to be removed. Suldes disappear during the magnetic separation. Phosphates only become vuseful for the process after a longer treatment at 650 C. with alkalines or alkalinerbauxite residues and by Wash- `ing out the trinatriumorthophosphate, NaPO, before the producing of fy-FezOs.

` Coal will not be absorbed by the iron at bare anneal- `ing conditions and at the low temperatures of the process.

'Ihe formation of small pellets with coal for facilitation of the furnace process, e.g., while manufacturing manganese (Mn) ores, is possible. At the iinal treatment of iron powder with about 0.1% of Na2CO3 will be suitably added above 600 C. With the remaining amounts and ashes of coal it can easily be automatically ground and magnetically separated.

Well known materials which accelerate the reduction, such as wood dust, lime milk and water vapour, might be added. Especially at the end of the reduction water vapour is wanted for removing the carbonaceous coatings.

What I claim is: l

l. A process for the production of pure iron from brown magentic iron oxide, 'y-FezOs, in which nelydivided 'y-Fe203 is contacted with a nely-divided carbonaceous reductant at a temperature' in the range of from 350 C. to 540 C., comprising mixing and contacting said finely-divided y-FezOa with reducing gas to uidize said 'y-Fe203, introducing the resultant mixture into the top of a reduction zone within a vertical furnacelike closed reduction chamber at a plurality of points distributed over the horizontal area of the reduction zone, mixing finely-divided carbonaceous reductant with reducing gas, intermittently introducing the resultant second mixture into said reduction zone in more than one horizontal areafthereof by blowing said second mixture ina vertical upward direction from a plurality of points distributed over each of said horizontal areas, the points on each of said areas being disposed below and staggered from the points on the area immediately above, whereby said first mixture falling down through said reduction z on'e 4is suspended above each of said horizontal areas by the upward blowing second mixture and dropped to the next lower horizontal area by intermittently stoppingl the 'ow of saidsecond mixture at eachv of said areas, thereby 4 l intimately contacting said first mixture with said second mixture and slowly transporting said lrst mixture continuously from the top of said reduction zone to the bottom of said reduction zone, and cooling the reduced material at the lower part of said reduction bone within the vertical furnacelike closed chamber to a temperature below C.

2. A process for the production of pure iron from brown magnetic iron oxide, y-FezOg, and another iron composition selected from the group consisting of hematite, magnetite and mixtures thereof, in which finely-div vided y-Fe203 Vand said other iron composition in finelydivided form are contacted with a nely divided carbonaceous reductant, comprising mixing said finely-divided `'y-FezOa with said other finely divided iron composition to twice the Weight `of 'y-FezOs, mixing and contacting said mixture with reducing gas to uidize said mixture, introducing the resultant tluidized-mixture into the top of a reduction zone within a vertical furnace-like closed reduction chamber at a plurality of points distributed over the horizontal area of this reduction zone, mixing nely-divided carbonaceous reductant with reducing gas, intermittently introducing the resultant second uidized mixture into said reduction zone in more than one horizontal area thereof by l'blowing said second liuidized mixture in vertical upward direction from a plurality of points distributed over each of said horizontal areas, the points on'each of said areas being disposed below and staggered from the points on the area immediately above,

whereby said rst uidized mixture falling down through said reduction zone is suspended above each of said horizontal areas by the upward blowing second fluidized mixture and dropped to the next lower horizontal area by intermittently stopping the flow of said second fluidized mixture at each `of said area, thereby intimately contacting said rst fluidized mixture with said second Eluidized mixture and slowly transporting said rst fluidized mixture continuously from the top of said reduction zone to the bottom of said reduction zone, and cooling the reduced material at the lower part of said reduction zone within the vertical furnace-like closed chamber to a temperatureV below 100 C.

3. A process for the production of pure iron from brown magnetic iron oxide, fy-Fe2O3, and another iron composition from the group consisting of hematite, magnetite and mixtures thereof, 'in which finely-divided 'y-FeZOa and said other iron composition in nely-divided form ,are contacted with a inely-divided carbonaceous reductant, comprising mixing said finely-divided y-Fe203 with said other nely-divided iron composition up to twice the weight of 'y-Fe2O3 and timely-divided carbonaceous reductant, pelletzing said mixture at a temperature below 200 C., mixing and contacting said pelletized mixthereof by blowing said second liuidized mixture in verl ticalupward direction from a plurality of points distributed over each of said horizontal areas, the points on each of said areas being disposed below and staggered r from the points on the area immediately above, whereby 'said 'rst fluidzed mixture falling down through said reduction zone is suspended above each of said horizontal areas by the upward blowing second uidized mixture and dropped to the Vnext lower horizontal area by intermittently stopping the ow of said second fluidized mixture at eachof said areas, thereby intimately contacting -said iirst iluidized mixture with said second uidized mix-v ture and slowly transporting said first iluidized lmixture .Gontinuously from the top of said reduction zone to the bottom of said reduction zone, and cooling the reduced material at the lower part of said reduction zone within the vertical furnace-like closed chamber to a temperature below 100 C.

References Cited in the le of this patent 6 Wilson Oct. 27,1931 Lykken Nov. 2, 1943 Brassert et al. Nov. 20, 1945 Hulthen June 3, 1952 Crowley Aug. 30, 1955 Gilliland Apr. 17, 1956 Ogoxzaly Apr. 17, 1956 Von Haken May 29, 1956 

1. A PROCESS FOR THE PRODUCTION OF PURE IRON FROM BROWN MAGNETIC IRON OXIDE Y-FE2O3, IN WHICH FINELYDIVIDED Y-FE2O3 IS CONTACTED WITH A FINELY-DIVIDED CARBONACEOUS REDUCTANT AT A TEMPERATURE IN THE RANGE OF FROM 350*C. TO 540*C., COMPRISING MIXING AND CONTACTING SAID FINELY-DIVIDED Y-FE2O3 WITH REDUCING GAS TO FLUIDIZED SAID Y-FE2O3, INTRODUCING THE RESULTANT MIXTURE INTO THE TOP OF A REDUCTION ZONE WITHIN A VERTICAL FURNACELIKE CLOSED REDUCTION CHAMBER AT A PLURALITY OF POINTS DISTRIBUTED OVER THE HORIZONTAL AREA OF THE REDUCTION ZONE, MIXING FINELY-DIVIDED CARBONACEOUS REDUCTANT WITH REDUCING GAS, INTERMITTENLY INTRODUCING THE RESULTANT SECOND MIXTURE INTO SAID REDUCTION ZONE IN MORE THAN ONE HORIZONTAL AREA THEREOF BY BLOWING SAID SECOND MIXTURE IN A VERTICAL UPWARD DIRECTION FROM A PLURALITY OF POINTS DISTRIBUTED OVER EACH OF SAID HORIZONTAL AREAS, THE POINTS ON EACH OF SAID AREAS BEING DISPOSED BELOW AND STAGGERED FROM THE POINTS ON THE AREA IMMEDIATELY ABOVE, WHEREBY 